The present invention relates to an interlayer placed on cracked roads to repair them. More specifically, this interlayer includes a mixture of aggregate and preferably polymer modified asphalt that is used to delay or stop the occurrence of cracking, control crack severity, reduce overlay thickness, and enhance waterproofing capabilities.
When pavements deteriorate, they may be overlaid with hot mix asphalt (HMA) to repair them. When designing an overlay, the rate of crack propagation through the overlay, the rate of deterioration of the reflective crack, and the amount of water that can infiltrate through the cracks must be considered. One disadvantage with such HMA overlays is that cracks in the old pavement reflect through the new overlay. To relieve this reflective cracking, thicker overlays must be placed. Another disadvantage with such HMA overlays is that they are permeable allowing water to enter the base. A third disadvantage with these overlays is that they typically have a low strain tolerance and a low resistance to reflective cracking.
Asphalt binders which display the ability to undergo creep or stress relaxation at low temperatures in order to minimize the potential for thermal and reflective cracking may be created. The disadvantage with such binders is that they are highly ductile, and thus, roads created with them tend to rut.
Asphalt binders with a high shear modulus that resist rutting at high temperatures may also be created. The disadvantage with such binders is that they tend to be brittle at low temperatures, and thus, roads created with them tend to crack. Typical asphalt binders formulated for pavement applications usually display either high shear modulus at high temperatures or high ductilities at low temperatures but not both.
Other reflective crack control measures that are used to rehabilitate distressed Portland Cement Concrete (PCC) pavements include placing stress-absorbing membrane interlayers (SAMI), placing grids or fabrics as an interlayer before placing HMA, break and seat of PCC, rubblization of PCC, and reconstruction. One disadvantage with these processes is that they can be expensive. Another disadvantage with these processes is that if the road is not reconstructed, it may still have cracking problems.
In order to overcome these disadvantages, an overlay that is able to slow reflective cracking without rutting and protect the pavement structure is needed. Still further, this overlay should be easy to apply and provide a smooth riding surface.